The benefits derived from comparative medical research are only beginning to be appreciated. Osler's concept of "One Medicine" and the use of animal models for comparative medical research has been philosophically proposed for many years, but only in the past decade have we appreciated the vast array of naturally occurring disorders in animals which are counterparts of similar human diseases. The objectives of this project are to find, identify and obtain animals with genetically determined diseases and to compare their alterations with those found in similar human diseases, to share information, tissues, samples, semen from affected or carrier animals, and animals with other investigators and finally to evaluate the potential usefulness and practicality of various animal models of human disease. Specific models of human disease currently under investigation include: Ehlers-Danlos syndrome, dysostosis, immunodeficiency disorders, Chediak-Higashi syndrome, a variety of neuromuscular disorders, lysozyme deficiency, progressive epilepsy, hyperreninism, malignant melanoma and juvenile-type diabetes mellitus.